The document discusses HMRC's use of customer insight and open policy making approaches. It provides examples of how HMRC has used tools like customer closeness, customer journey mapping, randomized controlled trials, and behavioral insights to inform policy making. One example discussed how customer research helped simplify the process for charities to file gift aid repayments online. The document also discusses how behavioral experiments with letter wording significantly increased tax debt repayment rates. Overall, the document advocates that incorporating customer perspectives and testing approaches can help improve policies and outcomes.